Concentrating module and method of manufacture for photovoltaic strips

ABSTRACT

A glass concentrator for manufacture of solar energy conversion module is provided including a webbing that has a load sustenance characteristic and a hail impact resistance characteristic based on a first thickness of the webbing. The concentrator also includes a plurality of elongated concentrating elements integrally formed with the webbing. Each of the elongated concentrating elements has an aperture region, an exit region and two side regions, which bears a geometric concentration characteristic provided by a highly reflective side regions and an aperture-to-exit. scale ratio in a range from about 1.8 to about 4.5. The glass concentrator can be attached with a plurality of photovoltaic strips cumulatively on each and every exit regions and clamped with a rigid or flexible back cover member to form a solar concentrator module for converting sunlight to electric energy. The solar concentrator module based on certain embodiments meets the industrial qualification standards.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority of U.S. patent application Ser. No.60/939,089, and titled “CONCENTRATING MODULE AND METHOD OF MANUFACTUREFOR PHOTOVOLTAIC STRIPS,” filed by Kevin R. Gibson at May 21, 2007commonly assigned, and is incorporated by reference in its entirety.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH OR DEVELOPMENT

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REFERENCE TO A “SEQUENCE LISTING,” A TABLE, OR A COMPUTER PROGRAMLISTING APPENDIX SUBMITTED ON A COMPACT DISK.

NOT APPLICABLE

BACKGROUND OF THE INVENTION

The present invention relates generally to solar energy techniques. Inparticular, the present invention provides a method and resulting devicefor manufacturing the solar energy conversion system. More particularly,the present invention provides a method and a structure for manufactureof a sunlight concentrator module having a glass webbing integrallyincluding a plurality of concentrating elements coupled with a pluralityof photovoltaic strips. Merely by way of example, the invention has beenapplied to solar panels, commonly termed modules, but it would berecognized that the invention has a much broader range of applicability.

As the population of the world increases, industrial expansion has leadto an equally large consumption of energy. Energy often comes fromfossil fuels, including coal and oil, hydroelectric plants, nuclearsources, and others. As merely an example, the international EnergyAgency projects further increases in oil consumption, with developingnations such as China and India accounting for most of the increase.Almost every element of our daily lives depends, in part, on oil, whichis becoming increasingly scarce. As time further progresses, an era of“cheap” and plentiful oil is coming to an end. Accordingly, other andalternative sources of energy have been developed.

Concurrent with oil, we have also relied upon other very useful sourcesof energy such as hydroelectric, nuclear, and the like to provide ourelectricity needs. As an example, most of our conventional electricityrequirements for home and business use comes from turbines run on coalor other forms of fossil fuel, nuclear power generation plants, andhydroelectric plants, as well as other forms of renewable energy. Oftentimes, home and business use of electrical power has been stable andwidespread.

Most importantly, much if not all of the useful energy found on theEarth comes from our sun. Generally all common plant life on the Earthachieves life using photosynthesis processes from sun light. Fossilfuels such as oil were also developed from biological materials derivedfrom energy associated with the sun. For human beings including “sunworshipers,” sunlight has been essential. For life on the planet Earth,the sun has been our most important energy source and fuel for modernday solar energy.

Solar energy possesses many characteristics that are very desirable!Solar energy is renewable, clean, abundant, and often widespread.Certain technologies developed often capture solar energy, concentrateit, store it, and convert it into other useful forms of energy.

Solar panels have been developed to convert sunlight into energy. Asmerely an example, solar thermal panels often convert electromagneticradiation from the sun into thermal energy for heating homes, runningcertain industrial processes, or driving high grade turbines to generateelectricity. As another example, solar photovoltaic panels convertsunlight directly into electricity for a variety of applications. Solarpanels are generally composed of an array of solar cells, which areinterconnected to each other. The cells are often arranged in seriesand/or parallel groups of cells in series. Accordingly, solar panelshave great potential to benefit our nation, security, and human users.They can even diversify our energy requirements and reduce the world'sdependence on oil and other potentially detrimental sources of energy.

Although solar panels have been used successful for certainapplications, there are still certain limitations. Solar cells are oftencostly. Depending upon the geographic region, there are often financialsubsidies from governmental entities for purchasing solar panels, whichoften cannot compete with the direct purchase of electricity from publicpower companies. Additionally, the panels arc often composed of siliconbearing wafer materials. Such wafer materials are often costly anddifficult to manufacture efficiently on a large scale. Availability ofsolar panels is also somewhat scarce. That is, solar panels are oftendifficult to find and purchase from limited sources of photovoltaicsilicon bearing materials. These and other limitations are describedthroughout the present specification, and may be described in moredetail below.

From the above, it is seen that techniques for improving solar devicesis highly desirable.

BRIEF SUMMARY OF THE INVENTION

The present invention relates generally to solar energy techniques. Inparticular, the present invention provides a method and resulting devicefor manufacturing the solar energy conversion system. More particularly,the present invention provides a method and a structure for manufactureof a sunlight concentrator module having a glass webbing integrallyincluding a plurality of concentrating elements coupled with a pluralityof photovoltaic strips. Merely by way of example, the invention has beenapplied to solar panels, commonly termed modules, but it would berecognized that the invention has a much broader range of applicability.

In a specific embodiment, the present invention provides a concentratorfor manufacture of solar energy conversion module. The concentratorincludes a webbing having a shape characterized by a first dimension, asecond dimension, and a planar region defined by the first dimension andthe second dimension. The webbing has a front region, a back region, anda first thickness provided between the front region and the back region.Additionally, the concentrator includes a load sustenance characteristicfrom the first thickness of the webbing. The load is at least of 2400 Pauniformly applied on the front region for 1 hour in two cycles. Theconcentrator further includes a hail impact resistance characteristic ofthe webbing. The impact hail is an ice ball with at least of 25 mmdiameter directed at a speed of at least 23 meter per second to at least11 locations of the front region. Moreover, the concentrator includes aplurality of elongated concentrating elements integrally formed with theback region one-next-to-another in parallel along the first dimension.Each of the elongated concentrating elements having a length, anaperture region, an exit region, a first side region provided between afirst portion of the aperture region and a first portion of the exitregion, a second side region provided between a second portion of theaperture region and a second portion of the exit region, and a secondthickness provided between the aperture region and the exit region. Thelength of the concentrating element is substantially the same as thesecond dimension. The concentrator further includes a geometric opticalconcentration characteristic provided by a scale ratio of the apertureregion to the exit region for each of the plurality of elongatedconcentrating elements. The scale ratio is characterized by a range fromabout 1.8 to about 4.5. Furthermore, the concentrator includes anoptical transparency characteristic of the first thickness of thewebbing combined with the second thickness of each of the plurality ofconcentrating elements with a transmissivity being at least of 90percent and greater within a visible light range. Of course, there canbe other variations, modifications, and alternatives. For example, thewebbing can be a glass or a plastic.

In an alternative specific embodiment, the invention provides a sunlightconcentrator module for manufacture of solar energy conversion system.The solar concentrator module including a webbing having a shapecharacterized by a first dimension, a second dimension, a planar regiondefined by the first dimension and the second dimension. The webbing hasa front region, a back region, and a first thickness of about 3 mm toabout 9 mm measured between the front region and the back region.Additionally, the module includes a load sustenance characteristicprovided by the first thickness of the webbing. The load is at least of2400 Pa uniformly applied on the front region for 1 hour in two cycles.The module further includes a hail impact resistance characteristic ofthe webbing with the first thickness. The impact hail can be an ice ballwith at least of 25 mm diameter directed at a speed of at least 23 meterper second to at least 11 locations of the front region. Moreover, themodule includes a plurality of concentrator elements integrally formedwith the back region excluding a peripheral region of the webbing. Eachof the concentrator elements is disposed one-next-to-another in parallelalong the first dimension and characterized by a length, an apertureregion, an exit region, a first side region provided between a firstportion of the aperture region and a first portion of the exit region, asecond side region provided between a second portion of the apertureregion and a second portion of the exit region, and a second thicknessof about 1.8 mm provided between the aperture region and the exitregion. The length of the concentrating element is substantially thesame as the second dimension. The module also includes a geometricconcentration characteristic provided by a scale ratio of the apertureregion to the exit region for each of the plurality of concentratorelements. The scale ratio is in a range from about 1.8 to about 4.5. Themodule further includes an Optical transparency characteristic of thefirst thickness of the webbing combined with the second thickness ofeach of the plurality of concentrating elements with a transmissivitybeing at least of 90 percent and greater within a visible light range.The module still includes a plurality of photovoltaic strips. Each ofthe plurality of photovoltaic strips is coupled to at least a portion ofeach of the exit region of the plurality of concentrator elements. Eachphotovoltaic strip has a width substantially similar to the exit region.One or more photovoltaic strips have a cumulative length substantiallysimilar to the length of the concentrator element. Furthermore, themodule includes a plurality of electric conducting leads disposed alongtwo edges of each of the plurality of photovoltaic strips. Each of theplurality of conducting leads is conductively connected to each otherand to module external electrical ports. The module further includeseither a rigid back cover or a flexible backsheet configured tomechanically couple with the webbing at the peripheral region.

In yet still an alternative embodiment, the present invention includes amethod of making a glass concentrator for manufacture of solar energyconversion module. The method includes forming molten glass. The methodthen includes feeding a predetermined amount of the molten glass into afloat bath to form a floating ribbon glass in rectangular shape definedby a first dimension and a second dimension, and processing the floatingribbon glass to have an even first thickness between a top surface and aback surface. Additionally, the method includes rolling with a shapedmolding roller across the top surface partially into the first thicknessof the floating ribbon glass at a predetermined first temperature withina first time period to form a plurality of shaped concentrating elementswith a second thickness. The method further includes annealing theribbon glass by gradually reducing temperature from the firsttemperature to a second temperature within a second time period. Themethod further includes lifting the ribbon glass at the secondtemperature onto a plurality of circular rollers and rolling the backsurface while continuing cool the ribbon glass to a third temperatureduring transportation on the plurality of circular rollers. The methodalso includes flame polishing the plurality of shaped concentratingelements on the top surface.

In a further alternative embodiment, the invention also provides amethod of making a glass concentrator for manufacture of solar energyconversion module. The method includes forming a ribbon glasscharacterized by a first thickness between a top surface and a backsurface. The method further includes rolling with a shaped moldingroller across the top surface partially into the first thickness of theribbon glass at a first temperature within a first time period to form aplurality of shaped structures with a second thickness. Additionally,the method includes polishing at least partially the plurality of shapedstructures on the top surface. In one embodiment, the first thicknesscomprises a characteristic of sustaining at least a load of 2400 Pauniformly applied for 1 hour in two cycles. In another embodiment, theplurality of shaped structures comprises a plurality of concentratingelements one-next-to-another in parallel. Each of the plurality ofconcentrating elements comprises two reflective side surfaces and ascale ratio of an aperture region to an exit region being about 2.0 andgreater. In yet another embodiment, the two reflective side surfaces arepolished with a root-mean-square roughness equal to 30 nm or less.

Still further, the present invention provides a method of assembling asolar concentrator module. The method includes preparing a glassconcentrator including a webbing. The webbing has a flat front plane anda back plane occupied entirely by a plurality of elongated concentratingelements excluding a peripheral region. Each of the plurality ofelongated concentrating elements has a light-collecting exit region.Additionally, the method including providing an optical couplingmaterial overlaying each light-collecting exit region. The methodfurther includes providing a plurality of photovoltaic strips. Each ofthe plurality of photovoltaic strips has two short sides and two longedges. The two short sides have comparable dimensions as thelight-collecting exit region. The two long edges include a plurality ofelectric leads that are inter-connected. Moreover, the method includesbonding the plurality of photovoltaic strips using at least the opticalcoupling material individually and cumulatively to each and everylight-collecting exit region. The method further includes providing aback cover member comprising a circuit board electrically coupled withthe plurality of electric leads. The back cover member has a shapesubstantially matched with the webbing and an integral uprising edgewall. Furthermore, the method includes clamping the edge wall with theglass concentrator at the peripheral region of the webbing.Alternatively, a flexible backsheet can be used in place of a rigid backcover.

Many benefits are achieved by way of the present invention overconventional techniques. For example, the present technique provides aneasy to use process that relies on conventional technology such assilicon materials in the photovoltaic strips, although other materialsalso can be used. Additionally, the method provides a process that iscompatible with conventional process technology without substantialmodifications to conventional equipment and processes. Preferably, theinvention provides for an improved solar module, which is less costlyand easy to handle. Such solar module uses a single piece of glasswebbing integrally including a plurality of concentrating elements forcoupling with a plurality of photovoltaic strips, which are packaged bycoupling a rigid back cover member around a peripheral region. In apreferred embodiment, the invention provides a glass concentrator havinga characteristic from the thickness of the glass webbing to sustain aload of at least 2400 Pa uniformly applied on the webbing surface for 1hour in two cycles. Also in a preferred embodiment, the inventionprovides a glass concentrator having a geometric concentrationcharacteristic with an aperture-to-exit scale ratio in a range fromabout 1.8 to about 4.5 and polished side regions with RMS roughness lessthan 30 nm. The use of concentrator according to the present inventionhelps the solar conversion module having less photovoltaic material persurface area (e.g., 80% or less, 50% or less) than conventional solarpanel module. In another preferred embodiment, the invention provides asunlight concentrator module packaged with a plurality of concentratingelements integrally formed with the glass webbing and coupled with aplurality of photovoltaic strips with improved total conversionefficiency. In still a preferred embodiment, the invention provides aconducting leads design reducing non-solar-conversion area within theassembly to enhance the packing factor to 90% or greater. In oneembodiment, the invention provides a solar concentrator module with aglass webbing as a top cover sealed with a rigid back cover or aflexible backsheet around the peripheral region. In another embodiment,the invention provides a solar concentrator module with a glass webbingas a top cover assembled with a rigid back cover or a flexible backsheetthat is not sealed so as to allow trapped water vapor breathing out ofthe photovoltaic region. Depending upon the embodiment, one or more ofthese benefits may be achieved. These and other benefits will bedescribed in more detail throughout the present specification and moreparticularly below.

Various additional Objects, features and advantages of the presentinvention can be more fully appreciated with reference to the detaileddescription and accompanying drawings that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagram illustrating a perspective view of aglass concentrator for a solar concentrator module according to anembodiment of the present invention;

FIG. 2 is a detailed diagram of a glass concentrator with a plurality ofelongated concentrating elements according to an embodiment of thepresent invention;

FIG. 3 is simplified diagram illustrating a method of making a glassconcentrator according to an embodiment of the present invention;

FIG. 4 is a simplified diagram illustrating a concentrating element withan exit region in reduced width and two side regions being flamepolishing treated according to an embodiment of the present invention;

FIG. 5 is a simplified diagram illustrating a method of assembling asolar concentrator module according to an embodiment of the presentinvention;

FIG. 6 is a simplified diagram illustrating an expanded view of a solarconcentrator module assembly according to an embodiment of the presentinvention; and

FIG. 7 is a simplified diagram illustrating an expanded view of a solarconcentrator module assembly according to an alternative embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates generally to solar energy techniques. Inparticular, the present invention provides a method and resulting devicefor manufacturing the solar energy conversion system. More particularly,the present invention provides a method and a structure for manufactureof a sunlight concentrator module having a glass webbing integrallyincluding a plurality of concentrating elements coupled with a pluralityof photovoltaic strips. Merely by way of example, the invention has beenapplied to solar panels, commonly termed modules, but it would berecognized that the invention has a much broader range of applicability.

FIG. 1 is a simplified diagram illustrating a glass concentrator for asolar concentrator module according to an embodiment of the presentinvention. This diagram is merely an example, which should not undulylimit the scope of the claims herein. One of ordinary skill in the artwould recognize other variations, modifications, and alternatives. Asshown is a perspective view of a glass concentrator, which is a lightconcentrator including a webbing and a plurality of concentratingelements. The concentrator 100 has a webbing with a top region 101 (notdirectly seen), back region 103, a first thickness 105 defined betweenthe top region and the back region, a first dimension 107, and a seconddimension 109. Additionally, a plurality of elongated concentratingelements 200 is formed integrally with the back region 103 of thewebbing as part of a single piece of glass. In one embodiment, each ofthe plurality of elongated concentrating elements has a length 110 andis disposed one-next-to-another in parallel extending from one sideportion of the webbing to another side of the webbing. In a specificembodiment, the elongated concentrating element is parallel to the sideof webbing with the first dimension. In another specific embodiment, theelongated concentrating element is parallel to the side of webbing withthe second dimension. In yet another embodiment, the plurality ofconcentrating elements 200 occupies the entire area of the back region103 excluding a peripheral region 115. Of course, there can be othervariations, modifications, and alternatives. The detail structures ofthe elongated concentrating element will be described in specificationbelow.

In a preferred embodiment, the webbing and the plurality ofconcentrating elements are made of a single piece of glass. For example,this piece of glass comprises mixed batch materials of sand, limestone,cerium oxide, iron oxide and salt cake. In one embodiment, the glasscomprises a concentration of iron content about a trace amount and less.In another embodiment, the glass has cerium oxide at a concentration ofabout a trace amount and less, or non-existent. In another preferredembodiment, the glass is a tempered glass, processed to meet safetystandard enforced by general construction codes. Of course, there can beother variations, modifications, and alternatives.

According to another embodiment of the present invention, theconcentrator as shown in FIG. 1 is directly used for manufacture a solarconcentrator module. In particular, the concentrator has a rectangularshape easy for manufacture and use. The rectangular shape ischaracterized by the first dimension 107 and the second dimension 109.In one embodiment, the first dimension 107 is selected to be about 1meter or bigger and the second dimension is correspondingly selected tobe about 1.6 meters or bigger. In another embodiment, with such a sizeselected above, the peripheral region 115 of about 10 mm in dimension isselected for clamping or other packaging purpose. Of course, there canbe other variations, modifications, and alternatives for the dimensionsselected for the concentrator.

As a preferred embodiment of the present invention, the concentrator 100will be directly used as a light receiving top cover member for thesolar conversion module. In order to satisfy the industry qualificationstandard regarding to module's mechanical toughness, the first thickness105 between the top region and the back region is selected to be atleast 3.2 mm according to an embodiment of the present invention. Forexample, the first thickness can be 5 mm. In another example, the firstthickness can be 6 mm. In yet another example, the first thickness canbe about 7.2 mm or larger. Such the selection of the first thickness 105provides an important load sustenance characteristic and impact hailresistance characteristic to the concentrator of the solar module,although other factors including the composition profile, stressprofile, packaging method etc also contribute to these physicalcharacteristics. For example, in one embodiment, the glass can bereplaced by a laminated glass made of polymer which may provide betterimpact resistance with a same or smaller thickness compared to aconventional solar glass.

According to Industrial Qualification Standards, the solar module shouldbe able to sustain a load of 2400 Pa uniformly applied to the surface ofthe module for 1 hour in two cycles. Additionally, the solar moduleshould be able to resist a hail impact represented by an ice ball of 25mm diameter directed at a speed of at least 23 meter per second to 11(random) locations on a entire surface region of about 1 meter×1.6 meteror bigger. According to certain embodiments, the combination of theselection of those physical dimensions and compositions of the glassconcentrator result in a satisfaction of all the IndustrialQualification Standards including the mentioned load test or impact hailtest. For example, Industrial Qualification Standards for solar moduleinclude TEC 61215, IEC 61730, and UL 1703. Of course, there can be othervariations, modifications, and alternatives for these dimension numbersincluding the first dimension, second dimension, the first thickness,and the peripheral region dimension.

Additionally, as part of a light receiving top cover, the concentratorreferred in the FIG. 1 must possess a high transmission and lowreflection characteristics. In one embodiment, the concentrator is madeof glass having a transparent characteristic with a transmissivity of 90percent and greater for a visible light range. This high transmissivityis achieved by controlling the composition of the glass to reduce thesunlight absorption to minimum. For example, the iron content of theglass needs to be a trace amount and less. In another example, ceriumoxide with a concentration of about a trace amount or less ornon-existent. In another embodiment, there will be an anti-reflectivecoating (not shown in FIG. 1) overlying the top region 101 which is aflat surface. In yet another embodiment, before applying theanti-reflective coating, an infrared blocking coating (not shown inFIG. 1) may be applied overlying the top region 101. This infraredblocking coating allows visible light transmitted through but block theinfrared spectrum so as to reduce the heating to the photovoltaic regionduring the sunlight conversion process. Of course, there can be othervariations, modifications, and alternatives.

FIG. 2 is a detailed diagram of a glass concentrator with a plurality ofelongated concentrating elements according to an embodiment of thepresent invention. This diagram is merely an example, which should notunduly limit the scope of the claims herein. One of ordinary skill inthe art would recognize other variations, modifications, andalternatives. As shown is a local cross-sectional view of the elongatedconcentrating elements integrally formed with the back region of thewebbing. Each of the concentrating element includes at least thefollowing geometric elements: an aperture region 201, an exit region203, a first side region 207 provided between a first edge portion 211of the aperture region and a first edge portion 215 of the exit region,a second side region 209 provided between a second edge portion 213 ofthe aperture region and a second edge portion 217 of the exit region,and a second thickness 205 measured between the aperture region 201 andthe exit region 203. A second edge portion for a first concentratingelement 200 a coincides with a first edge portion of the neighboringsecond concentrating clement 200 b to form an aperture notch. Forexample, an aperture notch is located at the edge portion 213. In oneembodiment, because there is a radius of curvature for each of theaperture notches (not shown in FIG. 2), the true aperture region 201 issubtracted by a small curved vicinity of two neighboring aperturenotches at edge portion 211 and 213. Similarly, the exit notch also hasa small radius of curvature so that true light exit region shouldinclude those curved exit notches. For example, exit region 203 shouldinclude two exit notches at edge portion 215 and 217. The apertureregion 201 is not an interface but an integral part of the back region103 of the webbing 100.

For effectively collecting the sunlight, the concentrating element ispreferred to possess a geometric optical concentrating characteristic.In a specific embodiment, the aperture region 201 is characterized by alight entrance area A2 and the exit region 203 is characterized by alight exit area A1. In an specific embodiment, the light entrance areaA2 includes only the true aperture region excluding a small curved areaof the aperture notch. The light exit area A1 should include additionalarea contributed by the curved exit notches. The light concentratingcharacteristic is represented by an aperture-to-exit area ratio A2/A1ranging from about 1.8 to about 4.5. In one embodiment, theaperture-to-exit area ratio is equivalent to a scale ratio as one sideof the aperture region 201 has a substantially equal dimension of oneside of the exit region 203. In other words, the exit region 203 has areduced dimension compared to the aperture region 201 and the two sideregions 207 and 209 of the concentration elements are tilt inward(relative to vertical direction). Sunlight coming through the apertureregion 201 with a relatively wide range of incident angles will becompletely reflected at the two side regions because those incidentangles (around the normal incident angle) may still be larger than thetotal reflection angle of the side region interface. In a specificembodiment, the second thickness 205 is selected to be about 1.8 mm andthe exit region width is about 2 mm and the aperture region width isabout 4.12 mm. In one embodiment, each of the two side regions may be aflat type of interface so that the cross-sectional view of theconcentrating element is a trapezoidal shape. In another embodiment,each of the two side regions may be curved type of interface withvariable curvature values across the spatial of side regions. In yetanother embodiment, the curvature variations of the two side regions maybe symmetric. In yet still another embodiment, the curvature variationsof the two side regions may be non-symmetric. Of course, there can beother variations, modifications, and alternatives.

In another specific embodiment, this light concentrating characteristicis also represented by high reflectivity of the inner face of the twoside regions. Firstly, the high reflectivity is achieved by polishingthe glass at the two side regions so that the roughness of the sideregion is reduced to a value of 30 nm RMS and less. Secondly, certainthin film coating may be applied to enhance the reflectivity. Of course,there can be other variations, modifications, and alternatives.

In yet another specific embodiment, this light concentratingcharacteristic is further implemented by certain roughening treatment tothe exit region to reduce the inner reflection at the exit region tominimum. This treatment may allow most sunlight beams reaching at theexit region be able to transmit through and be received by aphotovoltaic strip that may be attached below the exit region in thesolar concentrator modules. In one embodiment, the photovoltaic stripcan be attached to the exit region using an optical adhesive. Forexample, the optical adhesive can be an aliphatic polyurethane. inanother embodiment, this optical adhesive can be chosen to have anoptical refractive index that well matches with the glass concentratingelement so that the reflection loss at the interface of exit regionwould be minimized. The refractive index of the glass concentrator is atleast 1.4 or greater. For example, the optical adhesive can be a twopart mixture using a aliphatic polyurethane mixture.

In yet still another specific embodiment, the light concentratingcharacteristic also can be represented by other geometric details suchas micro-curvature near the vicinities of the aperture notches 211 and213 and exit notches 215 and 217. A smaller radius of curvature for theaperture notch helps to increase effective light entrance area. Asmaller radius of curvature for the exit region help to reduce thepossible loss of light collected from being directed away from thephotovoltaic strips. Certain embodiments of the present inventioninclude a method of making the glass concentrator with minimized notchradius of curvature for each of the plurality of concentrating elements.For example, the radius of curvature for the notches of theconcentrating element is about 0.1 mm or less. With a reduced notchradius of curvature, the light concentrating efficiency is improved. Ofcourse, there can be other variations, modifications, and alternatives.All these physical, mechanical, and optical properties of theconcentrating clement cumulatively contribute the performance of thelight concentrating function for manufacture of an efficient andcost-effective solar conversion module according to certain embodimentsof the present invention.

Further detail of various methods according to embodiments of thepresent invention on making the glass concentrator and assembling asolar concentrator module are provided throughout the presentspecification and more particularly below.

According to a specific embodiment, a method for making the glassconcentrator for manufacture of solar conversion module can be outlinedas follows:

1. Forming a ribbon glass in a floating bath with a rectangular shapeand a first thickness between a front surface and a back surface;2. Rolling with a shaped molding roller across the front surfacepartially into the first thickness to form a plurality of shapedstructures;3. Annealing the ribbon glass;4. Rolling the back surface while transporting the ribbon glass;5. Polishing at least partially each of the plurality of shapedstructures.

These sequences of processes provide a way of performing a methodaccording to an embodiment of the present invention. As shown,embodiments of the present invention provides a easy way of integrallymaking the glass webbing with a plurality of elongated concentratingelements possessing necessary light concentration function while at thesame time bearing other characteristics required for an efficient solarenergy conversion module that meets all industrial qualificationstandards. The method can be implemented based on establishedconventional floating glass manufacturing technology. The flamepolishing treatment also provides a low cost high quality process forachieving the required small roughness for certain portion of theconcentrating elements. Of course, there can be variations,modifications, and alternatives. Some processes can be performed indifferent order. Some processes can be removed or added. For example,when using plastic material to replace glass, some process may bemodified to use direct molding to form the elongated concentratingelements. Alternative polishing processes may also be utilized toachieve required roughness and minimized notch radius. These and otherdetails of the present method can be found throughout the presentspecification and more particularly below.

FIG. 3 is simplified diagram illustrating a method 300 of making a glassconcentrator according to an embodiment of the present invention. Thisdiagram is merely an example, which should not unduly limit the scope ofthe claims herein. One of ordinary skill in the art would recognizeother variations, modifications, and alternatives. As shown, the method300 includes forming a ribbon glass (process 311) in a floating bathwith a rectangular shape and a first thickness between a top surface anda back surface. In one embodiment, a group of batch materials includingsand, limestone, cerium oxide, iron oxide and salt cake are collected,then melted and blended in a furnace. In another embodiment, the moltenglass is made from polymer. The resulting product is a molten glass withcontrolled compositions of certain materials that bears the requiredphysical characteristics including photon absorption, mechanicalstrength, stress distribution, or refractive index value etc. Of course,there can be other variations, modifications, and alternatives.

Depending on the embodiment, the method 300 may include feeding apredetermined amount of the molten glass or semi-fluid polymer into afloating bath. The floating bath typically can be made of tin withpolished surface at its bottom and peripheral sides having a desiredrectangular dimensions and a depth. For example, the rectangulardimensions are substantially the same as the first dimension or thesecond dimension of the webbing mentioned earlier in this specification.In a specific embodiment, the floating bath is provided with aprotective atmosphere consisting of a mixture of nitrogen and hydrogento prevent oxidation of the tin. As being feed in the floating bath, themolten glass spreads to entire bath spatially due to the gravity andsurface tension.

Depending on the embodiment, the method 300 may include processing theribbon glass to have a first thickness even for entire ribbon glassbetween a top surface and a back surface. For example the processinginvolves to control the temperature of the floating glass so that it canspread to entire bath due to the gravity and proper surface tension. Inanother example, the processing includes rolling the top surface tospeed up the spreading or stretching of the floating glass. According tocertain embodiments, the first thickness is necessary for possessingsufficient load sustenance and impact hail resistance characteristicsfor the resulting glass webbing to be used for manufacture of a solarconcentrating module. For example, the first thickness is at least 5 mm.In another example, the first thickness is about 8 to 9 mm. Theprocessing the ribbon glass also includes annealing the ribbon glass andcooling it to a desired temperature for a molding process.

Additionally, the method 300 includes rolling (process 321) with ashaped molding roller across the front surface partially into the firstthickness to form a plurality of shaped structured with a secondthickness. The molding roller is at least longer than one dimension ofthe ribbon glass in rectangular shape. The rolling process may beperformed after the formation of ribbon glass with the even firstthickness and the temperature of the subject ribbon glass is cooled to apredetermined first temperature. Depending upon the embodiment, themethod may includes lowering a shaped molding roller with a elongatedbody and a predefined cross-sectional shape, aligning the roller inparallel with one side of the rectangular-shaped ribbon glass, rollingthe roller across the top surface partially into the first thickness ofthe ribbon glass, then re-lifting away from the top surface within afirst time period. In a specific embodiment, the lowering and rolling ofthe molding roller is controlled to generate a second thickness for theplurality of shaped structures during the rolling process. In anotherspecific embodiment, the rolling process comprises a cooling procedurethat uses a cooling system following after the roller. The coolingsystem provides a localized cooling for the just-formed structures onthe top surface. For example, the cooling system may spray a pulse ofcold water or cryogenic non-reactive gas locally. The localized coolinghelps to partially fix the shaped structures formed from the rollingprocess. In a preferred embodiment, the plurality of shaped structureson the top surface are a series of elongated elements substantiallyidentical to each other. Each of the elongated elements comprises anoptical concentrating geometry characterized by two side surfaces and ascale ratio of an aperture region to an exit region larger than at least2.0. The plurality of shaped concentrating elements are formedone-next-to-another with a second thickness on the top surface of theribbon glass. In another preferred embodiment, the second thicknessformed by the rolling process for each concentrating element is about1.8 mm. The remaining portion of the ribbon glass belongs to thewebbing.

Moreover, the method 300 includes annealing the ribbon glass (process331) to gradually cool the entire ribbon glass. Right after aconcentrating element is formed, a localized cooling is applied forpartially fix the shape of the concentrating element. During thatprocedure, the temperature of the ribbon glass may be cooled locallyfrom the first temperature to a second temperature via conduction andconvention. After the rolling process, the entire ribbon glass may befurther annealed using another cooling system. The annealing process iscontrolled to cool the ribbon glass from the second temperature from athird temperature within a second time period. Depending on theembodiment, the annealing process helps to reduce the stress within theribbon glass and improve the load sustenance and impact resistance ofthe resulting glass webbing.

As the ribbon glass is sufficiently cooled, the method 300 may includelifting the ribbon glass out of the floating bath and transfer to aplurality of circular rollers coupling with the back surface. The ribbonglass can be transported in the process 341 along the roller pathway toa polishing treatment stage. Then the process 351 can be executed usingan elongated burner that is burning with hydrogen and oxygen gas mixturewith a predetermined mixing ratio. The elongated burner with a flame isdirected to the top surface containing the plurality of elongatedconcentrating elements formed in the rolling process (321). Theorientation of the burner is substantially aligned with each of theplurality of formed concentrating elements. Particularly, the burner isconfigured to generate flames with a narrow, nearly one-dimensionalshape so that relatively small region of the concentrating element canbe treated with better control. For example, the formed concentratingelement is the elongated concentrating element 200 that has two sidesurfaces 207 and 209. The flame polishing treatment is controlled toapply only on the side surfaces 207 and 209 but not on the exit region.In one embodiment, each side surface is treated at a time while theburner is directed sequentially from one side surface to another andfrom one concentrating element to next. In another embodiment, the flametreatment may also be used to adjust radius of the exit notches 215 and217 etc. or reduce the radius of curvature of the aperture notches 211and 213 etc. In yet another embodiment, the flame on/off, flametemperature, flame polish time, queue time, and other process parameterscan be controlled by a controller linked with a computer so that thedesired roughness of the two side regions or desired exit radius can beachieved. For example, as low as 30 nm RIMS and less for two sideregions is preferred. Of course, there can be many other variations,modifications, and alternatives.

The method 300 also includes rolling the back surface (process 341)while annealing and transporting the ribbon glass. Before and after theflame polishing process, the ribbon glass can be rolled on its backsurface by a plurality of rollers. The rolling serves to flattening theback surface while transporting the subject glass during which the glasscontinues to be annealed to room temperature.

Although the method 300 has been specifically shown by those processsteps mentioned in above paragraphs, there can be many other variations,modifications, and alternatives. Some of the processes may be removed orbe performed in different order. Other processes may be added or used toreplace some of above processes. For example, the rolling process usinga shaped molding roller for forming the concentrating elements may bereplaced by using a shaped cast molding directed into the secondthickness into the ribbon glass with a first thickness. Alternatively,an etching process may be used for forming the plurality ofconcentrating elements. In another example, the flame polishing processmay be replaced by an acid polishing or a mechanical process. In yetanother example, plastic material can be used to replace glass for theconcentrator. Fixed molding can be used instead of roller and otherpolishing techniques such as vapor polishing and mechanical polishingmay be used in addition to the flame polishing. Additionally, one ormore post-deposition processes may be performed to overlay infraredblocking coating on the back surface (which will become the front regionfor the solar module) when the ribbon glass is transferred to adeposition chamber. Furthermore, an anti-reflective coating may bedeposited overlying the infrared blocking coating. The side regions ofthe concentrating elements can also be deposited with a reflectivityenhancement coating.

FIG. 4 is a simplified diagram illustrating a concentrating element withan exit region in reduced width and two side regions being flamepolishing treated according to an embodiment of the present invention.This diagram is merely an example, which should not unduly limit thescope of the claims herein. One of ordinary skill in the art wouldrecognize other variations, modifications, and alternatives. As shown,one elongated concentrating element 200 has a side region 207 andanother side region 209. An elongated burner 401 having substantiallysimilar length as the concentrating element 200 is aligned insubstantially the same orientation. The burner 401 is configured to havea plurality of gas nozzles (not shown directly in FIG. 4).Hydrogen/oxygen gas mixture is supplied though a build-in tubing in theburner holder. As ignited, the plurality of gas nozzles is capable ofgenerating a nearly one-dimensional flame 403. In one embodiment, thegas mixing ratio is predetermined to generate a desired heat transferprofile along the axial direction of the flame. The burner 401 with theflame 403 is directed to the vicinity of the concentrating element 200at a predetermined variable distance. The flame 403 touches the sideregion 207 to perform the polishing treatment. In another embodiment,the burner 401 is configured to rotate in certain range of angles 405 sothat it can be guided to the one side region at a proper angle at onetime and then be guided with a proper angle to the next side region atanother time. In yet another embodiment, the burner 401 can be laterallytransported in direction 407 to allow the polishing treatment beingperformed from one concentrating element to another. In certainembodiments, multiple burners that are similar to the burner 401 can beimplemented at the same time to speed up the treatment for all theconcentrating elements on the whole concentrator. Of course, dependingupon the embodiment, there can be many other variations, modifications,and alternatives.

In an alternative embodiment, the invention provides a method forassembling a solar concentrating module as illustrated by FIG. 5.Preferably, the method can be implemented using the glass concentratormade according to certain embodiments of the present invention. A method500 according to an embodiment of the present invention can be outlinedas follows:

1. Process 510: preparing a concentrator comprising a webbing with aplurality of elongated concentrating elements having light-collectingexit regions;2. Process 520: providing an optical coupling material overlaying thelight-collecting exit regions;3. Process 530: providing a plurality of photovoltaic strips;4. Process 540: bonding the plurality of photovoltaic strips using atleast the optical coupling material to the light-collecting exitregions;5. Process 550: providing a back cover member, wherein the back covermember can be rigid or flexible;6. Process 560: clamping the back cover member with. the webbing;7. Process 570: performing other steps, as desired.

These sequences of processes provide a way of performing a methodaccording to an embodiment of the present invention. As can be seen, themethod provides a technique for assembling a solar concentrator moduleusing the concentrator made according to another embodiment of theinvention. Of course, there can be variations, modifications, andalternatives. Some processes can be performed in different order. Someprocesses can be removed or added. For example, clamping a rigid backmember with the planar webbing of the glass concentrator is performeddifferently from clamping a flexible backsheet with the webbing. Afterthe clamping the back cover member with the webbing, a sealing processmay be performed. In another example, the clamped package comprisinghollow space between the photovoltaic strips and the back cover memberwill not be sealed, instead, air or other vapor is allowed to breathin/out. Further details of the present method and resulting structurescan be found throughout the present specification and more particularlybelow.

Referring now to FIG. 6, an expanded view of a solar concentrator moduleassembly according to an embodiment of the present invention isillustrated. This diagram is merely an example, which should not undulylimit the scope of the claims herein. One of ordinary skill in the artwould recognize other variations, modifications, and alternatives. Asshown in FIG. 6, a solar concentrator module includes various elements.The module has a glass concentrator 610, which is a planar webbingincluding a front region, a back. region, a shape characterized by afirst dimension and a second dimension, and a first thickness providedbetween the front region and the back region. The front region is a flatsurface which is also a top surface of the module for receiving thesunlight. The back. region integrally includes a plurality of elongatedconcentrating elements. Each of the elongated concentrating elementsincludes a light-collecting exit region. For example, the glassconcentrator 610 is a planar webbing glass with shaped concentratingelements made from the method of 300 referred in FIG. 3. In one example,the planar webbing has a planar region comprising a rectangular shapedpanel with the first dimension about 1 meter or bigger and a seconddimension about 1.6 meter or bigger. As an example, for assembling asolar concentrator module, the glass concentrator 610 may be prepared bythe process 510.

In a preferred embodiment, the plurality of elongated concentratingelements is characterized by a geometric optical concentrating function.In one embodiment, the concentrating function is represented by anelongated exit region with a reduced dimension versus a light entrancearea corresponding to each concentrating element. Each of the elongatedconcentrating elements joins with one or two neighboring element to forman aperture notch. An aperture notch with minimized radius of curvaturehelps to maximize the true size of aperture region, i.e., the lightentrance area. In another embodiment, the concentrating function isrepresented by the two highly reflective side regions for each of theelongated concentrating element that help to direct light coming in theaperture region to the exit region with minimum loss. In anotherpreferred embodiment, the exit region is a second distance away from theback region of the planar webbing. The plurality of elongatedconcentrating elements cumulatively occupies the entire back regionexcept a peripheral region surrounding the planar webbing.

An optical coupling material 620 is provided overlaying the spatial areaof the exit region for each and every elongated concentrating elements.The optical coupling material will be used for bonding the concentratingelement with the solar energy conversion unit. For example, the opticalcoupling material is aliphatic polyurethane. In a preferred embodiment,the optical coupling material has a refractive index of about 1.4 orgreater that is well matched with the glass concentrator used for thisassembly. The matching of the refractive index will ensure minimum lossof the collected light beam from being reflected from the interfacebetween the exit region and the coupling material. Additionally, thecoupling material is desired to have a suitable Young's Modulus and athermal expansion coefficient so that the coupling material canwithstand for changes due to thermal expansion of both the glass elementand photovoltaic strip element. For example, the optical couplingmaterial is a aliphatic polyurethane, but can be others. As an example,the optical coupling material 620 is provided in process 520.

Referring to FIG. 6 again, the solar concentrator module furtherincludes a plurality of photovoltaic strips 630. These photovoltaicstrips are formed on a semiconductor substrate and are cut into a stripshape defined by two short sides with a strip width and two long edgeswith a strip length. In one embodiment, the strip width is about 2 mmwhich is substantially the same as a preferred width of the exit region.The strip length is about 6 inches. Each of the photovoltaic stripsincludes a plurality of p-type regions and a plurality of n-typeregions. Each of the p-type regions is coupled to at least one of then-type regions to form a p-n junction unit capable of converting photoenergy to electricity. For example, the photovoltaic strips are made ofat least one material selected from single crystal silicon,polycrystalline silicon, amorphous silicon, copper indium diselenide(CIS), Copper Indium Gallium Selenide (CIGS), Cadmium Telluride (CdTe),thin film materials, or nanostructured materials. Of course, there canbe other variations, modifications, and alternatives. As an example, theplurality of photovoltaic strips is provided in process 530.

As an example, the solar concentrating module includes a plurality ofphotovoltaic strips spatially disposed in a parallel manner overlayingthe exit regions of the elongated concentrating elements. Each of thephotovoltaic strips is operably bounded with at least a portion of oneexit region by the optical coupling material 620. In one embodiment, thelength of an exit region of the concentrating element is about 1 meteror bigger. Multiple photovoltaic strips are required to attach with theexit region one following another and cumulatively covers all spatialarea of the exit region. Similarly, a plurality of photovoltaic stripsare attached with each and every exit region of the plurality ofconcentrating elements. Of course, there can be other variations,modifications, and alternatives. As an example, the plurality ofphotovoltaic strips are bounded with corresponding concentratingelements in process 540.

In a preferred embodiment, each of the photovoltaic strips comprises aplurality of electric leads located on two long edges. Each of theplurality of electric leads is coupled to each other through thinconductive wires. Additionally, conductive means including but notlimiting bus bars are used for coupling the neighboring photovoltaicstrips. These electric leads and conductive means are configured to linkto an electric circuit for providing electric power that is generatedfrom the sunlight by p-n junction units in the plurality of photovoltaicstrips. Of course, there can be other variations, modifications, andalternatives.

Further referring to FIG. 6, the solar concentrator module also includesa rigid back cover member 640. The back cover member includes a planarregion comprising a electric circuit board and a peripheral uprisingedge wall. The electric circuit board is configured for coupling withthe plurality of electric leads on each of the plurality of photovoltaicstrips and providing power management for module electric power output.The edge wall of the back cover member is configured to be easilyclamped with the webbing of the concentrator at the peripheral region.The edge wall has a properly selected height that is substantially suitfor enclosing the entire rest parts of the module including the glassconcentrator, the photovoltaic strips, circuit board and all couplingmaterials in between. In one embodiment, the back cover member 640 ischaracterized by an anodized aluminum bearing material. In anotherembodiment, the back cover member 640 is made of plastic material. Inyet another embodiment, the back cover member has a surface featureconfigured to provide efficient heat dissipation. For example, aplurality of fins may be formed on the outer surface of the back covermember. Of course, there can be other variations, modifications, andalternatives on the material selection and mechanical design for theback cover member. For example, the back cover member 640 is provided inprocess 550.

In a preferred embodiment, the back cover member 640 is clamped with theglass webbing of the concentrator 610. The glass webbing of theconcentrator 610 has an about 10 mm peripheral region being left outwithout the concentrating elements and intentionally designed for themodule packaging purpose. In one embodiment, the clamping can be donebased on mechanical mechanism using clips or screws etc. In anotherembodiment, the clamping is performed by welding the back cover memberand an encapsulating frame of the glass together. The edge wall of theback cover member is specifically designed to match with the peripheralregion of the glass webbing. In another embodiment, the clamping betweenthe back cover member and the rest of module is done by a glue-bondingmechanism. Depending on the embodiment, the resulting solar module fromany clamping mechanism contributes effectively to many characteristicsrelated to load sustenance, impact resistance, and ability to withstandenvironmental stress or aging. Of course, there can be other variations,modifications, and alternatives. As an example, the clamping of the backcover member 640 to the webbing is performed at process 560. Of course,there can be other variations, modifications, and alternatives.

In an alternative embodiment, the uprising surrounding wall of the backcover member has a height more than that required for enclosing all therest components of the solar concentrator module so that there are somespatial region between the photovoltaic strips and the back covermember. In one embodiment, after the clamping process, a sealing processmay be performed to add vacuum-tight encapsulate material around theclamping joint. The sealing encapsulate material is selected based onmodule qualification test requirement imposed for the solar module. Thequalification tests include damp heat test, humidity freeze test,thermal cycling test, UV or hot-spot tests or other aging tests. Thevacuum sealed packaging may have advantage to perform better to reducecertain types of damage related to moisture dropped onto thephotovoltaic strips. In another embodiment, the clamped package isintentionally left some micro passage ways to allow breathing, i.e.,during day time the heated spatial region between the photovoltaicstrips and the back cover member can drive out the absorbed moistureinside the module. Of course, there can be other variations,modifications, and alternatives.

In an alternative embodiment, referring to FIG. 7, the solarconcentrator module includes all components mentioned earlier exceptthat the rigid back cover member can be replaced by a flexible backsheet640′. FIG. 7 is just an exemplary illustrating of such solarconcentrator module including the flexible backsheet. The flexiblebacksheet is configured to adapt the surface corrugation after attachingthe plurality of photovoltaic strips to the concentrator elements.Additionally, the flexible backsheet, according to certain embodimentsof the invention, still is capable of providing the necessary mechanicalsupport and environmental protection for the solar concentrator module.In one embodiment, the flexible backsheet 640′ is also provided inprocess 550 and is clamped with the glass concentrator 610 in process560.

It is also understood that the examples and embodiments described hereinare for illustrative purposes only and that various modifications orchanges in light thereof will be suggested to persons skilled in the artand are to be included within the spirit and purview of this applicationand scope of the appended claims.

1. A method for making a glass concentrator for manufacture of solarenergy conversion module, the method comprising: forming a molten glass;feeding a predetermined amount of the molten glass into a float bath toform a floating ribbon glass in rectangular shape defined by a firstdimension and a second dimension; processing the floating ribbon glassto have an even first thickness between a top surface and a backsurface; rolling with a shaped molding roller across the top snakepartially into the first thickness at a predetermined first temperaturewithin a first time period to form a plurality of shaped concentratingelements with a second thickness; annealing the ribbon glass bygradually reducing temperature from the first temperature to a secondtemperature within a second time period; lifting the ribbon glass at thesecond temperature onto a plurality of circular rollers; rolling theback surface of the ribbon glass while continuing cool the ribbon glassto a third temperature during transportation on the plurality ofcircular rollers; flame polishing the plurality of shaped concentratingelements on the top surface; wherein, the feeding a predetermined amountof the molten glass comprises controlling the first thickness to atleast 5 mm to possess a characteristic of sustaining at least a load of2400 Pa uniformly applied for 1 hour in two cycles; rolling with ashaped molding roller across the top surface partially into the firstthickness to form a plurality of shaped concentrating elements with asecond thickness comprises forming a plurality of elongated structuresone-next-to-another in parallel, each of the plurality of elongatedstructures comprising a geometrical optical concentrating element with ascale ratio of an aperture region to an exit region greater than 2.0. 2.The method of claim 1 wherein the forming a molten glass comprisesmelting and blending batch materials including sand, limestone, ceriumoxide, iron oxide and salt cake in a furnace.
 3. The method of claim 1wherein the forming a molten glass comprises forming a polymer insemi-fluidic form.
 4. The method of claim 1 wherein the feeding apredetermined amount of the molten glass into a float bath comprisesforming a laminated structure by alternatively feeding molten glass withdifferent composition of materials.
 5. The method of claim 1 during therolling with a shaped molding roller across the top surface furthercomprises partially re-shaping the just-formed concentrating elementusing a localized water cooling or cryogenic gas cooling.
 6. The methodof claim 1 wherein the annealing the ribbon glass comprises cooling theentire ribbon glass via conduction and convection.
 7. The method ofclaim 1 wherein the flame polishing the plurality of shapedconcentrating elements comprises using a burner comprising a pluralityof gas nozzles to generate a nearly one-dimensional flames.
 8. Themethod of claim 7 wherein the burner includes a gas supply tubeconnected to a pressured gas tank comprising a gas mixture of hydrogenand oxygen with a predetermined mixing ratio.